Solid state relay

ABSTRACT

A compact solid state relay ( 7 ) is provided. Solid state devices ( 74, 75 ), such as Triacs or Thyristors are used to implement the relay functionality. The device is at least partially enclosed in a housing that has pins for mounting on an electronics board. A number of “U” shaped jumpers ( 72 ) or other jumpers or wires are provided in the housing to act as heat sinks. A subminiature fan ( 70 ) is positioned to create an air flow over the heat sinks and dissipate heat from the device.

CROSS-REFERENCES

This application is a nonprovisional of U.S. patent application No.61/792,576, entitled, “SOLID STATE RELAY,” filed Mar. 15, 2013, thecontents of which are incorporated herein by reference as set forth infull and priority from this application is claimed to the full extentallowed by U.S. law.

The following applications are incorporated by reference herein, thoughno priority claim is made:

-   1) U.S. Patent Application Publication No. US-2012/0181869-A1,    published on Jul. 19, 2012, entitled, “PARALLEL REDUNDANT POWER    DISTRIBUTION,” U.S. patent application Ser. No. 13/208,333, filed on    Aug. 11, 2011, entitled, “PARALLEL REDUNDANT POWER DISTRIBUTION,”    which is a nonprovisional of and claims priority from U.S.    Provisional Patent Application No. 61/372,752, filed Aug. 11, 2010,    entitled “HIGHLY PARALLEL REDUNDANT POWER DISTRIBUTION METHODS,” and    U.S. Provisional Patent Application No. 61/372,756, filed Aug. 11,    2010, entitled “REDUNDANT POWER DISTRIBUTION,”-   2) U.S. Pat. No. 8,004,115 from U.S. patent application Ser. No.    12/569,733, filed Sep. 29, 2009, entitled AUTOMATIC TRANSFER SWITCH    MODULE, which is a continuation-in-part of U.S. Pat. No. 12/531,212,    filed on Sep. 14, 2009, entitled “AUTOMATIC TRANSFER SWITCH,”, which    is the U.S. National Stage of PCT Application US2008/57140, filed on    Mar. 14, 2008, entitled “AUTOMATIC TRANSFER SWITCH MODULE,” which    claims priority from U.S. Provisional Application No. 60/894,842,    filed on Mar. 14, 2007, entitled “AUTOMATIC TRANSFER SWITCH MODULE;”    and-   3) U.S. Patent Application Publication No. US-2012-0092811 for U.S.    patent application Ser. No. 13/108,824, filed on May 16, 2011,    entitled “POWER DISTRIBUTION SYSTEMS AND METHODOLOGY,” is a    continuation of U.S. patent application Ser. No. 12/891,500, filed    on Sep. 27, 2010, entitled, “Power Distribution Methodology” which    is a continuation-in-part of International Patent Application No.    PCT/US2009/038427, filed on Mar. 26, 2009, entitled, “Power    Distribution Systems And Methodology,” which claims priority from    U.S. Provisional Application No. 61/039,716, filed on Mar. 26, 2008,    entitled, “Power Distribution Methodology.”

FIELD

Embodiments of the present invention relate to the use of small formfactor solid state relays in various contexts and providing innovativemethods to allow them to be incorporated into the design of small formfactors devices where space is limited and the shedding of the heatinherent to solid state relays is a significant issue. These types ofissues arise in the design of devices that are used in the design andoperation of data centers and, in particular, to devices used in thedistribution of power including such distribution in mission criticalequipment used in such environments as medical contexts, the powerutility grid or in data center environments.

BACKGROUND

Numerous products in the electronic marketplace utilize industrystandard relays in small form factor packages. An example relay of suchtype is referred to as the G2RL footprint, among other trade names.These small form factor footprints allow compact deployment of a varietyof medium power relays on Printed Circuit Boards (PCB) in a manner thatis efficient in volumetric deployment, and has pin spacing at or verynear the practical limits to be Agency accepted. Specifically, “Agency”refers to Underwriters Laboratories, or UL, and/or any other approvingagencies concerned with PCB copper trace placement and spacing. Thisminiature relay interconnection layout, being common within the industryis applicable to a wide variety of electro-mechanical relaycombinations. In some applications, the use of Solid State Relays (SSR)is desirable.

However, the use of SSRs in this miniature footprint has been restrictedto build-as-you-go methodology, and no defined package for a SSR in thisformat has been developed or recognized due to a simple problem -dissipating heat. In a traditional electro-mechanical relay of thissize, very little heat is generated, due to the mechanical contactshaving very little resistance. Typical heat generation by-productnumbers are less than a Watt when the electro-mechanical version ispassing its rated power. The rated power of the example G2RL relays thatare used as an example case in this invention would typically be 6 Ampsat 240 Volts. In addition, these relays are often in one of threeconfigurations. Industry references are Form A, Form B and Form C. FormsA and B are simply two contacts either connected together by activationor the relay, (Form A), two contacts either dis-connected from eachother by activation or the relay, (Form B), Or three contacts, one ofwhich is a common that is disconnected from one of the other contacts,and connected to the third contact when activated (Form C). Of these,this invention applies to all three forms, but is of primary concern tothe third, the Form C variety, as it is the most complex of the threevarieties.

SUMMARY

The present invention relates to providing methods to allow the use ofsmall form factor SSR relays in various contexts, including in datacenter environments. This can be an important issue because of thedifference in the transfer time of standard mechanical contact relaysvs. solid-state relays, which are much faster. Mechanical relays areusually constructed with the contacts mounted (usually on an armature)so that they can be moved to accomplish their switching function. Thecontact mass, shape, range of motion, mechanical leverage and force usedto move the armature are all relay design issues. The range of motion isdictated by the gap needed between the contacts to minimize arcing atthe maximum design current level and voltage rating. As the maximumdesign current is increased, the gap must also increase. The mass of thecontact must be accelerated by the force applied to the armature, whichhas a practical limit. These factors impose a limit on the amount ofcurrent that can be sent through a pair of contacts in a mechanicalrelay and still maintain an acceptable transfer time for EDP equipment.EDP equipment CBEMA guidelines recommend a maximum of approximately 20milliseconds of power outage for continued operation of modern switchedpower supplies. If the mass of the armature and contact gap are toolarge, the relay transfer time exceeds this time limit.

Solid State Relays do not have the transfer time limitations ofmechanical relays, they have transfer times that are generally fasterthan traditional mechanical relays. However, they are less efficient,they waste approximately 1-3% of the current that flows through them asheat, which is much more than traditional mechanical relays waste.

The invention relates to providing improved packaging methods for SSRrelays which allows them to be used in place of traditional standardsmall form-factor mechanical relays in a variety of contexts. They canbe used in the design of automatic transfer switches (ATS), forswitching between two or more power sources (e.g., due to power failuressuch as outages or power quality issues), as well as other powerdistribution components. Some of the objectives of the invention includethe following:

Providing methods to enable the of use of small form factor SSD relaysin the place of traditional standard small form-factor mechanicalrelays, particularly in devices that have small form factors andtherefore have not used such SSD relays due to issues with disposing ofthe extra waste heat that SSD relays produce relative to traditionalmechanical relays of the same rated capacity;

Providing methods to efficiently dispose of the additional waste heat;and

Providing options to design engineers to cost-effectively use theinvention in existing designs.

These objectives and others are addressed in accordance with the presentinvention by providing various systems, components and processes forimproving SSD relay packaging and deployment options. Many aspects ofthe invention, as discussed below, are applicable in a variety ofcontexts. However, the invention has particular advantages in connectionwith data center applications. In this regard, the invention providesconsiderable flexibility in designing devices that are used in powerdistribution and control in data center environments. The invention isadvantageous in designing the devices used in power distribution toserver farms such as are used by companies such as Google or Amazon orcloud computing providers.

In accordance with one aspect of the present invention, a method andapparatus (“utility”) is provided for a switching power. The utilityinvolves implementing a relay on a printed circuit board. The relay isoperative for switching power between a first contact associated withthe first circuit and a second contact. The relay is mounted on ahousing structure for at least partially enclosing the relay. Multipleheat sink elements are provided within the housing for dissipating heatgenerated by the relay in operation. For example, the heat sink elementsmay comprise “U” shaped jumpers formed from a heat conducting materialor other jumpers or wires extending between opposite sides of thehousing. The utility further includes a fan position for producing airflow across the heat sink elements. In a preferred implementation, asub-miniature fan is mounted on the housing to generate the air flow.

The invention disclosed can also be incorporated in a variety ofapparatus, for example such as described in U.S. patent application Ser.No. 13/108.824, filed on May 16, 2011, entitled, “POWER DISTRIBUTIONMETHODOLOGY.” This allows the creation of auto-switched powerdistribution methods that incorporate auto-switching as an integratedfeature of the power distribution methodology.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described in conjunction with the appendedfigures:

FIG. 1 shows a example of a typical G2RL mechanical relay as referencedin the discussion of the invention;

FIG. 2 shows the electrical configuration of a typical G2RL mechanicalrelay;

FIG. 3 shows an example G2RL SSD relay in accordance with the invention;

FIG. 4 illustrates a mechanical cross-section of an example G2RL SSDrelay in accordance with the invention;

FIG. 5 depicts a cross section of an example G2RL relay discussed inaccordance with the invention;

FIG. 6 depicts an alternate instantiation of the heat sinking jumpers inaccordance with the invention.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a second label thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the second reference label.

DETAILED DESCRIPTION

FIG. 1 depicts the mechanical outline of a traditionalelectro-mechanical relay of the example G2RL footprint. It should benoted that various footprints in this size category are possible, andthis representation is not restricted to this exact combination of sizeand dimensions. Observing FIG. 1, the dimensions of the package can beobserved and envisioned as miniature with respect to many availableelectro-mechanical relays on the market. The overall package size of 1.2inch by 0.6 inch by 0.5 inch is in the reasonably compact category forpower control relays. This package size is used extensively in industry,and in particular, in the system described in U.S. Pat. No. 8,004,115,issued on Aug. 23, 2011, entitled, “AUTOMATIC TRANSFER SWITCH MODULE.”

FIG. 1 depicts an orthogonal view (1) of the referenced relay packagewith end view (10), side view (12), top view (11), and a typical pin(13), often in various combinations of placement on the bottom of therelay, but generally with a pitch of 0.2 inch with respect to otherpins. The relay shown is of the Form C mentioned earlier. The relaydepicted in FIG. 1 also has two sets of Form C contacts.

FIG. 2 shows the electrical configuration of this relay:

It shows one set of the Form C contacts (2), with the parallel set (3).The Common contact (21), the Normally Closed (NC) contact (22) and theNormally Open (NO) contact (23). A coil (20) is utilized to change theposition of the two common contacts simultaneously.

FIG. 3 depicts the same relay with the schematic representation of theSolid State Relay components. FIG. 3 shows a schematic representation ofthe desired configuration referenced in this invention with the foursemiconductor Alternating Current (AC) control switches often calledTriacs (32, 33), or Thyristors. These semiconductor devices essentiallyreplace the contacts found in a traditional AC switching applications.In addition, the traditional coil is replaced with a control wire oneach of the Triacs (32, 33) called a Gate. These Gates (34, 35) are nowconnected to pins on the bottom of the Relay assembly.

Switch pair (4) is the equivalent to one of the Form C contactsmentioned in the traditional electro-mechanical relay, and switch pair(5) is the equivalent of the second of the Form C contacts mentioned inthe traditional electro-mechanical relay.

The principal limitation of the SSR is the heat generated. Solid Statesemiconductors including, but not limited to, triacs have a typicalvoltage drop across the two power conduction terminals of about 1.2Volts. This means that when current is running through thesemiconductor, the semiconductor is dissipating power at a rate of aboutthe current times the voltage drop, or, in the example relay case of 6Amps, 6 Amps times 1.2 Volts, or 7.2 Watts. This is not a great amountof heat, but in the confined space of the package dimensions of thedesired embodiment of this patent, it is very difficult to dissipate.The example presented here allows an easily manufactured means ofdissipating that heat, thus enabling the manufacture of the SSR inminiature form factors for universal replacement and use in place of theelectro-mechanical varieties. This is desirable to enable fasteractuation times, and better control of the timing of the admittance ofcurrent through the relay(s).

FIG. 4 depicts a mechanical layout cross section of a preferredembodiment of the invention:

In FIG. 4, it should be noted the overall mechanical dimensions of thepackage are the same as in the example provided for the miniatureelectro-mechanical equivalent. Of notable exception are two additionalelectrical mounting and conductors for the additional gate controlsmentioned, and apertures at the ends of the relay (6) to allow heat tobe expelled via air circulation.

FIG. 5 depicts a cross section of the example relay discussed inaccordance with this invention. It depicts the cross section (7) andorthogonal (8) views of a preferred embodiment of this invention.Observing the cross section the principal components of the SSR can beseen. As mentioned before, for each Form C switch equivalent, a pair ofSolid State devices (74, 75), such as triacs or thyristors, are used.The device package preferred for these Solid State devices is the JDECSOT482 package style, although it is possible to use other equivalent ornearly equivalent size packages. Also shown is a critical component, afan (70). These sub-miniature fans are now commercially available in apackage size of 10 mm by 8 mm by 3 mm, from various manufacturers. Theultra-miniature size of these mechanical fans allow the construction ofthis relay embodying the invention. Shown are copper “U” shaped jumpers(72) in numerous locations with the tips (73) of those jumpers (72)shown protruding through the Printed Circuit Board (71). The Solid StateSwitches (SSS) (74, 75) are surface mounted soldered to the interiorsurfaces of the PCBs (71) and have contiguous copper from under thoseSSS devices to the solder in points of the jumpers (72). This coppertrace is of a thickness selected to provide suitable heat transfer fromthe SSS devices (74, 75) to all of the jumpers (72) It should be notedthat each PCB shown has a total of 9 such jumpers (72), but more or lesscould be utilized, as well as the placement of the components could bearranged for better PCB layout, or more efficient heat transfer. Air,circulated by the fan (70) is drawn or pushed across all of thecomponents (74, 75, 80 to 84, 72) especially the jumpers (72) to removeheat.

One aspect of the invention consists of the novel application ofcurrently available standard jumpers used in the machine production ofPCB assemblies. Sufficient surface area can be acquired for veryefficient cooling of the SSS devices (74, 75) by simply inserting thedesired number of jumpers in various locations and possibly at variousdepths. The depth of insertion is a programmable item with modernautomated assembly machines. Thus, the completed sub-assembly consistingof a PCB (71), electronic components (74, 75, 80 to 84) and multiplecopies of heat sinking jumpers (72) can be accomplished in a single passon an automated PCB assembly machine, a process often called “stuffing”.

The final assembled relay can be covered by an injection molded cover,as shown in FIG. 3 (6) or left exposed without a cover for use inarrangements where the fan (70) is either replaced by, or supplementedwith external cooling air moved by an external source.

Additional electronic components (80 to 84) are shown for a possibleoption that allows electronic control for the gate drive of the SSSdevices (74, 75) such that only switching at the point where the appliedAC voltage passes through zero volts on each half cycle. This so-calledzero crossing control may be utilized to provide more contiguous andnon-harmonic switching. An additional benefit, and possibly requirementwill be that at no time can both SSS devices be turned onsimultaneously. The additional electronic components (80 to 84) are alsocapable of being arranged in a manner that prevents this occurrence.

FIG. 6 depicts an alternate instantiation of the heat sinking jumpers.In FIG. 6, it can be observed that the jumpers referenced in FIG. 5 (72)have been replaced by jumpers (90) proceeding between the two mainboards. This variation could be applied for applications where theelectrical components of each of the two SSR semiconductor groups havecommon electrical potentials. This application could be utilized toconstruct a single Form C relay with double the current carryingcapacity by sharing the current among two SSS devices, one of which islocated on each of the board subassemblies. This configuration alsoutilized wire jumpers machine insertable, and does not require specialheat sink sub-assemblies. In addition, the density of wire jumpers(preferably copper or aluminum), the placement of, and total number ofcan be selected to provide optimum heat transfer from the SSS devices tothe air.

It should be noted that both the “U” shaped jumpers and straight jumpersdescribed can have kinks, and other geometric variations to assist inimproving their heat transfer efficiency.

The foregoing description of the present invention has been presentedfor purposes of illustration and description. Furthermore, thedescription is not intended to limit the invention to the form disclosedherein. Consequently, variations and modifications commensurate with theabove teachings, and skill and knowledge of the relevant art, are withinthe scope of the present invention. The embodiments describedhereinabove are further intended to explain best modes known ofpracticing the invention and to enable others skilled in the art toutilize the invention in such, or other embodiments and with variousmodifications required by the particular application(s) or use(s) of thepresent invention. It is intended that the appended claims be construedto include alternative embodiments to the extent permitted by the priorart.

What is claimed:
 1. A relay device, comprising: a relay, implemented ona printed circuit board, operative for switching power between a firstcontact associate with a first circuit and a second contact; housingstructure for at least partially enclosing said relay; multiple heatsink elements for dissipating heat generated by said relay in operation,each of said heat sink elements comprising a jumper extending betweenfirst and second circuit board solder points; and a fan positioned forproducing an air flow across said heat sink elements.
 2. A relay deviceas set forth in claim 1, wherein said heat sink elements comprise “u”shaped jumpers formed from heat conducting material.
 3. A relay deviceas set forth in claim 1, wherein said heat sink elements are formed fromheat conducting material and extend between walls of said housing.
 4. Arelay device as set forth in claim 1, wherein said relay is implementedas solid state switches.
 5. A relay device as set forth in claim 1,where said fan is mounted on said housing.
 6. A relay device as setforth in claim 5, further comprising pins extending from said housingfor mounting on an electronics board.
 7. A relay device as set forth inclaim 1, further comprising a controller for controlling said relay toswitch power in synchronization with a phase of a power signal.
 8. Amethod for use in constructing a relay, comprising: forming a relay on aprinted circuit board, said relay operative for switching power betweena first contact associated with a first circuit and a second contact;mounting said relay on a housing structure for at least partiallyenclosing said relay; mounting multiple heat sink elements on saidhousing for dissipating heat generated by said relay in operationwherein said heat sink elements comprise jumpers and said mountingcomprises soldering each said jumper at first and second circuit boardsolder points; and positioning a fan so as to produce an air flow acrosssaid heat sink elements.
 9. A method as set forth in claim 8, whereinsaid step of mounting multiple heat sink elements comprises operating amachine to insert said heat sink elements to a desired depth.
 10. Amethod as set forth in claim 8, wherein said step of positioning a fancomprises mounting a fan on said housing.
 11. A method as set forth inclaim 8, wherein said relay includes pins extending from said housingand said method further comprises using said pins for mounting saidrelay on an electronics board.
 12. A method as set forth in claim 8,further comprising operating a controller for controlling said relay toswitch power and synchronization with zero crossings of a power signal.13. A relay device, comprising: a relay, implemented on a printedcircuit board, operative for switching power between a first contactassociate with a first circuit and a second contact; housing structurefor at least partially enclosing said relay; multiple heat sink elementsfor dissipating heat generated by said relay in operation; and a fanpositioned for producing an air flow across said heat sink elements,wherein said housing structure includes pins extending therefrom forenabling connections to said relay from an exterior of said housingstructure and further having apertures formed in one or more surfacesthereof to allow heat to be expelled via air circulation.
 14. A relaydevice as set forth in claim 13, wherein said heat sink elementscomprise “u” shaped jumpers formed from heat conducting material.
 15. Arelay device as set forth in claim 13, wherein said heat sink elementsare formed from heat conducting material and extend between walls ofsaid housing.
 16. A relay device as set forth in claim 13, wherein saidrelay is implemented as solid state switches.
 17. A relay device as setforth in claim 13, where said fan is mounted on said housing.
 18. Arelay device as set forth in claim 17, wherein said pins extending fromsaid housing are configured for mounting on an electronics board.
 19. Arelay device as set forth in claim 13, further comprising a controllerfor controlling said relay to switch power in synchronization with aphase of a power signal.
 20. A relay device as set forth in claim 13,further comprising thermally conductive traces for connecting said relayto said multiple heat sink members.